Microtubule polyglutamylation is an essential regulator of cytoskeletal integrity in Trypanosoma brucei.

Tubulin polyglutamylation, catalysed by members of the tubulin tyrosine ligase-like (TTLL) protein family, is an evolutionarily highly conserved mechanism involved in the regulation of microtubule dynamics and function in eukaryotes. In the protozoan parasite Trypanosoma brucei the microtubule cytoskeleton is essential for cell motility and for maintaining cell shape. In a previous study we showed that T. brucei TTLL6A and 12B are required to regulate microtubule dynamics at the posterior cell pole. Here, using gene deletion, we show that the polyglutamylase TTLL1 is essential for the integrity of the highly organised microtubule structure at the cell pole, with a phenotype distinct from that observed in TTLL6A/12B depleted cells. Reduced polyglutamylation in TTLL1-deficient cells also leads to increased levels in tubulin tyrosination, providing new evidence for an interplay between the tubulin tyrosination/detyrosination cycle and polyglutamylation. We also show that TTLL1 acts differentially on specific microtubule doublets of the flagellar axoneme, although the absence of TTLL1 appears to have no measurable effect on cell motility.